Justice Scalia
delivered the opinion of the Court.
When an alien is found ineligible to remain in the United States, the process for selecting the country to which he will be removed is prescribed by 8 U. S. C. § 1231(b)(2). The question in this case is whether this provision prohibits removing an alien to a country without the explicit, advance consent of that country’s government.
I
Petitioner Keyse Jama was born in Somalia and remains a citizen of that nation. He was admitted to the United States as a refugee, but his refugee status was terminated in 2000 by reason of a criminal conviction. See Jama v. INS, 329 F. 3d 630, 631 (CA8 2003). The Immigration and Naturalization Service (INS) brought an action to remove petitioner from the United States for having committed a crime involving moral turpitude. Ibid.; see 8 U. S. C. §§ 1182(a) (2)(A)(i)(I), 1229a(e)(2)(A). In the administrative hearing, petitioner conceded that he was subject to removal, although he sought various forms of relief from that determination (adjustment of status, withholding of removal, and asylum relief under the United Nations Convention Against Torture and Other Cruel, Inhuman, or Degrading Treatment or Punishment). He declined to designate a country to which he preferred to be removed. The Immigration Judge ordered petitioner removed to Somalia, his country of birth [338]*338and citizenship. The Board of Immigration Appeals affirmed that determination, and petitioner did not seek review in the Court of Appeals.
Instead, petitioner instituted collateral proceedings under the habeas statute, 28 U. S. C. §2241, to challenge the designation of Somalia as his destination. He filed his petition in the United States District Court for the District of Minnesota, alleging that Somalia has no functioning government, that Somalia therefore could not consent in advance to his removal, and that the Government was barred from removing him to Somalia absent such advance consent. The District Court agreed that petitioner could not be removed to a country that had not consented in advance to receive him, Jama v. INS, Civ. File No. 01-1172 (JRT/AJB) (Mar. 31, 2002), p. 10, App. to Pet. for Cert. 51a, but a divided panel of the Court of Appeals for the Eighth Circuit reversed, holding that § 1231(b)(2) does not require acceptance by the destination country, 329 F. 3d, at 633-635. We granted certiorari. 540 U. S. 1176 (2004).
II
Title 8 U. S. C. § 1231(b)(2), which sets out the procedure by which the Attorney General1 selected petitioner’s destination after removal was ordered, was enacted as follows:
“(2) Other aliens. — Subject to paragraph (3)—
“(A) Selection of country by alien. — Except as otherwise provided in this paragraph—
[339]*339“(i) any alien not described in paragraph (1) who has been ordered removed may designate one country to which the alien wants to be removed, and
“(ii) the Attorney General shall remove the alien to the country the alien so designates.
“(B) Limitation on designation. — An alien may designate under subparagraph (A)(i) a foreign territory contiguous to the United States, an adjacent island, or an island adjacent to a foreign territory contiguous to the United States as the place to which the alien is to be removed only if the alien is a native, citizen, subject, or national of, or has resided in, that designated territory or island.
“(C) Disregarding designation. — The Attorney General may disregard a designation under subpara-graph (A)(i) if—
“(i) the alien fails to designate a country promptly;
“(ii) the government of the country does not inform the Attorney General finally, within 30 days after the date the Attorney General first inquires, whether the government will accept the alien into the country;
“(iii) the government of the country is not willing to accept the alien into the country; or
“(iv) the Attorney General decides that removing the alien to the country is prejudicial to the United States.
“(D) Alternative country. — If an alien is not removed to a country designated under subparagraph (A)(i), the Attorney General shall remove the alien to a country of which the alien is a subject, national, or citizen unless the government of the country—
“(i) does not inform the Attorney General or the alien finally, within 30 days after the date the Attorney General first inquires or within another period of time the Attorney General decides is reasonable, whether the government will accept the alien into the country; or
“(ii) is not willing to accept the alien into the country.
[340]*340“(E) Additional removal countries — If an alien is not removed to a country under the previous subpara-graphs of this paragraph, the Attorney General shall remove the alien to any of the following countries:
“(i) The country from which the alien was admitted to the United States.
“(ii) The country in which is located the foreign port from which the alien left for the United States or for a foreign territory contiguous to the United States.
“(iii) A country in which the alien resided before the alien entered the country from which the alien entered the United States.
“(iv) The country in which the alien was born.
“(v) The country that had sovereignty over the alien’s birthplace when the alien was born.
“(vi) The country in which the alien’s birthplace is located when the alien is ordered removed.
“(vii) If impracticable, inadvisable, or impossible to remove the alien to each country described in a previous clause of this subparagraph, another country whose government will accept the alien into that country.
“(F) Removal country when United States is at war. — When the United States is at war and the Attorney General decides that it is impracticable, inadvisable, inconvenient, or impossible to remove an alien under this subsection because of the war, the Attorney General may remove the alien—
“(i) to the country that is host to a government in exile of the country of which the alien is a citizen or subject if the government of the host country will permit the alien’s entry; or
“(ii) if the recognized government of the country of which the alien is a citizen or subject is not in exile, to a country, or a political or territorial subdivision of a country, that is very near the country of which the alien is a citizen or subject, or, with the consent of the govern[341]*341ment of the country of which the alien is a citizen or subject, to another country.” Immigration and Nationality Act, § 241(b)(2), as added by the Illegal Immigration Reform and Immigrant Responsibility Act of 1996 (IIRIRA), § 305(a)(3), 110 Stat. 3009-600.
The statute thus provides four consecutive removal commands: (1) An alien shall be removed to the country of his choice (subparagraphs (A) to (Q), unless one of the conditions eliminating that command is satisfied; (2) otherwise he shall be removed to the country of which he is a citizen (sub-paragraph (D)), unless one of the conditions eliminating that command is satisfied; (3) otherwise he shall be removed to one of the countries with which he has a lesser connection (clauses (i) to (vi) of subparagraph (E)); or (4) if that is “impracticable, inadvisable, or impossible,” he shall be removed to “another country whose government will accept the alien into that country” (clause (vii) of subparagraph (E)). Petitioner declined to designate a country of choice, so the first step was inapplicable. Petitioner is a citizen of Somalia, which has not informed the Attorney General of its willingness to receive him (clause (i) of subparagraph (D)), so the Attorney General was not obliged to remove petitioner to Somalia under the second step. The question is whether the Attorney General was precluded from removing petitioner to Somalia under the third step (clause (iv) of subparagraph (E)) because Somalia had not given its consent.
A
We do not lightly assume that Congress has omitted from its adopted text requirements that it nonetheless intends to apply, and our reluctance is even greater when Congress has shown elsewhere in the same statute that it knows how to make such a requirement manifest. In all of subparagraph (E), an acceptance requirement appears only in the terminal clause (vii), a clause that the Attorney General may invoke only after he finds that the removal options presented in the [342]*342other six are “impracticable, inadvisable, or impossible.” Clauses (i) through (vi) come first — in the statute and in the process of selecting a country. And those six clauses contain not a word about acceptance by the destination country; they merely direct that “the Attorney General shall remove the alien” to any one of them.
Effects are attached to nonacceptance throughout the rest of paragraph (2), making the failure to specify any such effect in most of subparagraph (E) conspicuous — and more likely intentional. Subparagraph (C) prescribes the consequence of nonacceptance in the first step of the selection process; subparagraph (D) does the same for the second step; and clause (vii) of subparagraph (E) does the same for the fourth step.2 With respect to the third step, however, the Attorney General is directed to move on to the fourth step only if it is “impracticable, inadvisable, or impossible to remove the alien to each country described in” the third step. Nonacceptance may surely be one of the factors considered in determining whether removal to a given country is impracticable or inadvisable, but the statute does not give it the dispositive effect petitioner wishes.
Petitioner seizes upon the word “another” in clause (vii) as a means of importing the acceptance requirement into clauses (i) through (vi). He argues that if the last resort country is “another country whose government will accept the alien,” then the countries enumerated in clauses (i) through (vi) must also be “countries whose governments will accept the alien.” That stretches the modifier too far. [343]*343Just last Term, we rejected an argument much like petitioner’s, noting that it ran contrary to “the grammatical ‘rule of the last antecedent,’ according to which a limiting clause or phrase . . . should ordinarily be read as modifying only the norm or phrase that it immediately follows.” Barnhart v. Thomas, 540 U. S. 20, 26 (2003). There, a statute referred first to a claimant’s “previous work” and then to “any other kind of substantial gainful work which exists in the national economy”; under the rule of the last antecedent, we declined to read the limiting clause “which exists in the national economy” into the term “previous work.” Id., at 26-28 (emphasis deleted; internal quotation marks omitted); accord, FTC v. Mandel Brothers, Inc., 359 U. S. 385, 389-390 (1959). We thus did not treat “any other” as the “apparently connecting modifier” that the dissent here thinks “another” to be, post, at 355.3
[344]*344Nor does the structure of subparagraph (E) refute the inference derived from the last antecedent rule. Each clause is distinct and ends with a period, strongly suggesting that each may be understood completely without reading any further.4 And as we have already noted, it is not necessary to turn to the acceptance language of clause (vii) to find the conditions under which the Attorney General is to abandon the third step and move to the fourth, the last resort option of any willing country. The Attorney General must do so if in his judgment it would be “impracticable, inadvisable, or impossible to remove the alien to each country described in” clauses (i) to (vi). This allows the Attorney General to take both practical and geopolitical concerns into account when selecting a destination country (and accords with the similar flexibility to pass over inappropriate countries that the statute gives the Attorney General at the other steps, see infra, at 348). Petitioner’s reading would abridge that exercise of executive judgment, effectively deeming the removal of an alien to any country to be per se “impracticable, inadvisable, or impossible” absent that country’s advance acceptance, even though in many cases — such as this one — it is nothing of the sort. (Removing an alien to Somalia apparently involves no more than putting the alien on one of the regularly [345]*345scheduled flights from Dubai or Nairobi, and has been accomplished a number of times since petitioner’s removal proceeding began. App. 36-40 (declaration of detention enforcement officer Eric O’Denius).) Even without advance consultation, a country with a functioning government may well accept a removed alien when he is presented at the border or a port of entry; the absence of advance consent is hardly synonymous with impracticability or impossibility.5
B
Petitioner contends that even if no acceptance requirement is explicit in the text, one is manifest in the entire structure of § 1231(b)(2). The Attorney General may not remove an alien to a country under subparagraph (A) or (D) without that country’s consent, petitioner reasons, so he must be barred from circumventing that limitation by removing the same alien to the same country under subparagraph (E). The dissent rests its argument only on the existence of an acceptance requirement in step two (subparagraph (D)) and not in step one (subparagraphs (A) through (C)).6
[346]*346We note initially a point that applies to both petitioner’s and the dissent’s positions: The “circumvention” argument requires that the country the Attorney General selects at step three — here, the country of birth under clause (iv) — also be the country of citizenship that was disqualified at step two for failure to accept the alien. That will sometimes be true, yet the reason step three exists at all is that it will not always be true. (Indeed, in petitioner’s case, several of the clauses of subparagraph (E) describe Kenya, not Somalia.) Despite this imperfect overlap, petitioner and the dissent seek to impose an acceptance requirement on all removals under step three, in the name of preventing the Attorney General from “circumventing” step two in the cases where a step-three country is also the country of citizenship.
The more fundamental defect in petitioner’s argument, which appeals to a presumed uniformity of acceptance requirement throughout § 1281(b)(2), is that its premise is false. It is simply not true that the Attorney General may not remove an alien to a country under subparagraph (A) or (D) without that country’s consent. Subparagraph (C) specifies that the Attorney General “may disregard” the alien’s subparagraph (A) designation if the designated country’s government proves unwilling to accept the alien or fails to respond within 30 days. The word “may” customarily connotes discretion. See, e. g., Haig v. Agee, 453 U. S. 280, 294, n. 26 (1981). That connotation is particularly apt where, as here, “may” is used in contraposition to the word “shall”: The Attorney General “shall remove” an alien to the designated country, except that the Attorney General “may” disregard the designation if any one of four potentially countervailing circumstances arises. And examining those four circumstances reinforces the inappropriateness of reading “may” to mean “shall” in subparagraph (C): Would Congress really have wanted to preclude the Attorney General from removing an alien to his country of choice, merely because that country took 31 days rather than 30 to manifest its ac[347]*347ceptance? (Subparagraph (C), unlike subparagraph (D), offers no “reasonable time” exception to the 30-day rule.) Petitioner insists that a lack of advance acceptance is an absolute bar to removal, but offers no plausible way of squaring that insistence with the text of subparagraph (C).7
Nor does the existence of an acceptance requirement at the fourth and final step create any structural inference that such a requirement must exist at the third. It would be a stretch to conclude that merely because Congress expressly directed the Attorney General to obtain consent when removing an alien to a country with which the alien lacks the ties of citizenship, nativity, previous presence, and so on, Congress must also have implicitly required him to obtain advance acceptance from countries with which the alien does have such ties. Moreover, if the Attorney General is unable to secure an alien’s removal at the third step, all that is left is the last resort provision allowing removal to a country with which the alien has little or no connection — if a country can be found that will take him. If none exists, the alien is left in the same removable-but-unremovable limbo as the aliens in Zadvydas v. Davis, 533 U. S. 678 (2001), and Clark v. Martinez, post, p. 371, and under the rule announced in those cases must presumptively be released into American [348]*348society after six months. If this is the result that obtains when the country-selection process fails, there is every reason to refrain from reading restrictions into that process that do not clearly appear — particularly restrictions upon the third step, which will often afford the Attorney General his last realistic option for removal.
To infer an absolute rule of acceptance where Congress has not clearly set it forth would run counter to our customary policy of deference to the President in matters of foreign affairs. Removal decisions, including the selection of a removed alien’s destination, "may implicate our relations with foreign powers” and require consideration of “changing political and economic circumstances.” Mathews v. Diaz, 426 U. S. 67, 81 (1976). Congress has already provided a way for the Attorney General to avoid removals that are likely to ruffle diplomatic feathers, or simply to prove futile. At each step in the selection process, he is empowered to skip over a country that resists accepting the alien, or a country that has declined to provide assurances that its border guards will allow the alien entry.
Nor is it necessary to infer an acceptance requirement in order to ensure that the Attorney General will give appropriate consideration to conditions in the country of removal. If aliens would face persecution or other mistreatment in the country designated.under § 1231(b)(2), they have a number of available remedies: asylum, § 1158(b)(1); withholding of removal, § 1231(b)(3)(A); relief under an international agreement prohibiting torture, see 8 CFR §§ 208.16(c)(4), 208.17(a) (2004); and temporary protected status, 8 U. S. C. § 1254a(a)(1). These individualized determinations strike a better balance between securing the removal of inadmissible aliens and ensuring their humane treatment than does petitioner’s suggestion that silence from Mogadishu inevitably portends future mistreatment and justifies declining to remove anyone to Somalia.
[349]*349c
Petitioner points to what he describes as the “settled construction” of § 1231(b)(2), and asserts that Congress, in its most recent reenactment of the provision, should be deemed to have incorporated that construction into law. We think not. Neither of the two requirements for congressional ratification is met here: Congress did not simply reenact § 1231(b)(2) without change, nor was the supposed judicial consensus so broad and unquestioned that we must presume Congress knew of and endorsed it.
Removal is a new procedure created in 1996 through the fusion of two previously distinct expulsion proceedings, “deportation” and “exclusion.” IIRIRA, § 304(a)(3), 110 Stat. 3009-589, 8 U. S. C. § 1229a. Our immigration laws historically distinguished between aliens who have “entered” the United States and aliens still seeking to enter, (whether or not they are physically on American soil). See Leng May Ma v. Barber, 357 U. S. 185, 187 (1958). “The distinction was carefully preserved in Title II” of the Immigration and Nationality Act (INA): expelling an alien who had already entered required a deportation proceeding, whereas expelling an alien still seeking admission could be achieved through the more summary exclusion proceeding. Ibid.; see Landon v. Plasencia, 459 U. S. 21, 25-27 (1982) (cataloging differences between the two proceedings). Aliens who, like petitioner, were allowed into the United States as refugees were subject to exclusion proceedings rather than deportation proceedings when their refugee status was revoked. 8 CFR § 207.8 (1995).8
[350]*350The cases on which petitioner relies pertained to the INA’s deportation provision, the former 8 U. S. C. § 1253 (1952 ed.). United States ex rel. Tom Man v. Murff, 264 F. 2d 926 (CA2 1959); Rogers v. Lu, 262 F. 2d 471 (CADC 1958) (per curiam).9 In the two cited .cases, the Courts of Appeals barred deportation of aliens to the People’s Republic of China, a nation with which the United States at the time had no diplomatic relations, without that nation’s prior consent. Tom Man, supra, at 928 (reading the acceptance requirement in clause (vii) to cover clauses (i) to (vi) as well); Rogers, supra, at 471.10 During the same period, however, courts— including the Court of Appeals that decided Tom Man — were refusing to read an acceptance requirement into the exclusion provision, the former 8 U. S. C. § 1227 (1952 ed.). E. g., Menon v. Esperdy, 413 F. 2d 644, 654 (CA2 1969). Likewise, when Congress amended the exclusion provision to expand the list of possible destinations — adding three new categories and a fourth, last resort provision virtually identical to the last resort provision in current § 1231(b)(2)(E)(vii), see 8 U. S. C. § 1227(a)(2) (1982 ed.) — courts were generally skepti[351]*351cal of efforts to read the acceptance requirement back into the other clauses. E. g., Walai v. INS, 552 F. Supp. 998, 1000 (SDNY 1982); Amanullah v. Cobb, 862 F. 2d 362, 369 (CA1 1988) (Aldrich, J., concurring). But see id., at 365, and n. 4 (opinion of Pettine, J.).
In other words, IIRIRA forged the new removal procedure out of two provisions, only one of which had been construed as petitioner wishes.11 And even the supposed judicial consensus with respect to that one provision boils down to the decisions of two Courts of Appeals — one of which was only a two-sentence per curiam that considered step two, not step three. Rogers, supra, at 471; see n. 9, supra.12 In the context of new § 1231(b)(2), the acceptance requirement is “neither a settled judicial construction nor one which we would be justified in presuming Congress, by its silence, impliedly approved.” United States v. Powell, 379 U. S. 48, 55, n. 13 (1964) (citation omitted). Even notwithstanding the [352]*352contradictory interpretation of the BIA, see n. 10, supra, petitioner’s Circuit authority is too flimsy to justify presuming that Congress endorsed it when the text and structure of the statute are to the contrary.13
* * *
For the foregoing reasons, the judgment of the Court of Appeals is affirmed.
It is so ordered.